1. Field of the Invention
The present invention relates to an imaging device that takes an image of an energy beam such as an X-ray and to an imaging system including this imaging device.
2. Related Background Art
An imaging device using a charge coupled device (“CCD” hereinbelow) is one having superior energy resolution and position resolution. The CCD has superior detection efficiency to energy beams with a relatively low energy band (0.1 to 20 keV) known as soft X-rays and to visible light. However, the detection efficiency with respect to energy beams with a relatively high energy band (20 to 100 keV) known as hard X-rays is extremely low because silicon is used as a constituent material of the imaging device. As a result, when images of hard X-rays are taken by a CCD, a scintillator or the like must be used to convert the hard X-rays to scintillation light (visible light, for example) with an energy band that permits imaging by the CCD.
Japanese Patent Application Laid Open No. 2001-74845 discloses a technology for taking images of X-rays in a wide energy band. The imaging system (semiconductor device and radioactive beam imaging system) disclosed in this publication includes a CCD for imaging soft X-rays and a CsI scintillator for imaging hard X-rays.